16 THE VITAL FUNCTIONS. 



of the organs with which it is to be incorporated; and their 

 purpose being to assimilate the food as much as possible 

 to the nature of the organic body it is to nourish, all these 

 functions have been included under the term Assimila- 

 tion. 



The second series of vital functions comprise those which 

 are designed to convey the nutritive fluids thus elaborated, 

 to all the organs that are to be nourished by them. In the 

 more developed systems of organization this purpose is ac- 

 complished by means of canals, called vessels, through which 

 the nutritive fluids move in a kind of circuit: in this case the 

 function is denominated the Circulation. 



It is not enough that the nutritive juices are assimilated: 

 another chemical process is still required to perfect their ani- 

 malization, and to retain them in their proper chemical con- 

 dition for the purposes of the system. This third object is 

 accomplished by the function of Respiration. 



Fourthly, several chemical products, which are wanted in 

 different parts of the economy, are required to be formed 

 by a peculiar set of organs, of which the intimate structure 

 eludes observation; although we may perceive that in many 

 instances among the higher orders of beings, a special appa- 

 ratus of vessels sometimes spread over the surface of a 

 membrane, at other times collected into distinct masses, is 

 provided for that purpose. These specific organs are termed 

 glands, and the office performed by them, as well as by the 

 simpler forms of structure above mentioned, is termed Se- 

 cretion. 



Fifthly, similar processes of secretion are also employed 

 to carry off from the blood such animal products as may 

 have been formed or introduced into it, and may possess or 

 have acquired noxious properties. The elimination of these 

 materials, which is the office of the excretories, constitutes 

 the function of Excretion. 



Sixthly, changes may take place in various parts of the 

 body, both solid and fluid, rendering them unfit to remain 

 in their present situation, and measures must be taken for 



